‘I’ll be careful the way I say this,” says Judy Blume’s son, Lawrence. “There wasn’t a deep understanding, in the Hollywood community, of how incredibly popular she is. I mean, she’s sold 85 million books!”

So how many feature films have been made out of the author’s crazily beloved novels about the bewildering process of growing up, including “Are You There God? It’s Me, Margaret” (a preteen copes with her changing body), “Deenie” (a 13-year-old’s dream of being a model ends when she’s diagnosed with scoliosis) or “Forever” (a high school senior’s first sexual experiences)?

That would be zero.

Even in an age when young-adult movie adaptations dominate the box office, from “Harry Potter” to “Twilight” to “The Hunger Games,” somehow Blume’s tomes — treasured by generations of female readers — have been totally neglected by the film industry. It seems incomprehensible that there’s no big-screen version of “Tales of a Fourth Grade Nothing” or “Blubber” — the latter a bullying tale that’s perhaps never been more topical — but it’s true.

Until now, that is. Mother and son finally took matters into their own hands. The result is “Tiger Eyes,” arriving Friday.

Adapted from Blume’s 1981 novel, it tells the story of teenage Davey Wexler (Willa Holland), who moves from Atlantic City to Santa Fe with her mother (Amy Jo Johnson) and little brother (Lucien Dale) after her dad is shot to death during a robbery at the family’s convenience store.

Unbeknownst to Judy until several years ago, the book was always one of her son’s favorites. “I was absolutely shocked when he said that during a Q&A,” says the author, now 75.

“That’s my story,” Lawrence, 49, points out. “My parents split up, and I was in New Jersey, and I was torn from my father — he didn’t die, thankfully — and moved to this little town in New Mexico. That emotional roller coaster of having to start again, at that delicate age, really resonated with me. When I read it, I immediately thought, ‘I want to make this into a movie someday.’ ”

In 2009, the opportunity came: Lawrence would direct, and his mom would co-write, produce and be present for the entire process.

Of utmost importance to both was making sure the book’s fans weren’t disappointed — and could recognize all the little details they loved in the text.

“We wrote the screenplay together,” says Judy, “and I kept saying things like, ‘You know, if we don’t have Wolf give Davey a piece of fruit when they’re in the canyon, we’re going to hear about it.’ We both tried to stay as true to it, emotionally, as we could.”

Still, there are departures. In the book, Davey meets a young man named Wolf while she’s hiking; they forge a friendship, but he is only fleetingly present. In the movie, the role of Wolf (played by Tatanka Means) is substantially expanded — and Judy says she doesn’t know why she wrote it any other way.

“I can’t believe that when I wrote the book, I sent him away!” she says. “I thought, ‘What was I thinking?’ You could never send him away in the movie. He’s just too important.”

As for why it’s taken so long for Blume’s work to find its way to the cinema — there was a TV movie of “Forever” in the ’70s, and a short-lived “Fudge” series in the ’90s — Lawrence cites several reasons.

“She was focused on the writing — she didn’t have any ambitions to come to Hollywood and make movies,” he says. “But over the years, some wonderful filmmakers have come along. Gus Van Sant once said he’d love to do ‘Forever,’ and she said, ‘Great,’ and then he went on to other things, as they do.

“And she wanted to work with people who had a certain level of class. She was afraid that doing it badly would embarrass her, or her fans would get upset.”

Also, Judy adds, “I don’t think every book needs to be a movie. I’m not sure I would ever do ‘Margaret.’ That’s a book that’s so personal to so many people — a movie might just be setting up an audience for disappointment.”

Blume is extremely proud of her son’s rendition of “Tiger Eyes.” The only problem? Given its glaring lack of vampires, wizards and fights to the death, it’s a small-scale affair with no huge studio backing it.

“I was in a bookstore the other day, and all these young women heard I was there and came running up and wanted to take their pictures with me,” Judy says. “And not one of them knew there was a movie of ‘Tiger Eyes.’ That was very discouraging.”

But Blume is hopeful that positive word of mouth will change that. And she still knows how to make her brand of realism irresistible to young readers.

“Moms come up to me at book signings and describe how they’re telling their daughters, ‘These were my favorite books,’ ” she says. “I say, ‘Quit it! That’s the biggest turnoff!’

“You want to get them to read them, leave them around the house and every so often, say, ‘You’re not ready to read this yet.’ ”